Many cardiovascular diseases are characterized by disordered vascular function. Abnormalities in vascular smooth muscle cell (VSMC) tone are important in the pathogenesis of hypertension and atherosclerosis, but are not well understood. The long-term objective of this PPG is to understand the complex underlying molecular mechanisms that regulate vascular tone in health and disease. The fundamental hypothesis that will be tested is that loss of the normal function of the critical proteins that regulate vascular smooth muscle cell contraction and relaxation directly causes abnormal vasomotion and disorders of blood pressure regulation. The program we propose takes advantage of an extensive and well-developed infrastructure and ongoing collaborations between the Tufts-New England Medical Center Molecular Cardiology research Institute (MCRI), its NHLBI SCOR in Ischemic Heart Disease, the Framingham Heart Study, and the Housman Genomics Laboratory at MIT. Four projects are proposed: P1: "Genetics of Vasorelaxation and Cardiovascular Responses"; P2: "Mechanisms of PKG-mediated Vascular Relaxation"; P3: "BKca Channel Regulation by PKG in Vascular Smooth Muscle"; and P4: "Vascular Dysfunction as an Etiology of Hypertension" in Mouse Models. Three Cores are also proposed (Genomics; Mouse; Administrative). The VSMC proteins that are the specific focus of this proposal include three proteins that we show are essential for normal blood pressure: RGS2, the regulator of Gq-protein signaling; estrogen receptor a; and the BKca potassium channel (a and a subunits), as well as the two physiologically most relevant myosin phosphatase regulatory kinases, Rho Kinase (ROCK) and PKGIa, the effector of nitric oxide/cGMO. Genetically altered mice for PKGI, RGS2, ERa and the BKca channel all demonstrate vascular contractile abnormalities and hypertension. This PPG provides extensive preliminary data from human genomic studies, intact mice, mouse vascular rings, cultured human and mouse vascular cells, patch-clamping, signal transduction experiments, and detailed renal physiology. The ability of the assembled investigators to collaborate effectively is demonstrated throughout the proposal. An important corollary of the hypothesis to be tested is the concept that hypertension can arise from primary abnormalities of the VSMC proteins that regulate vascular relaxation. To formally test this hypothesis, targeted mutations in these critical VSMC regulatory genes are introduced into mice and sought in humans. The highly integrated studies of this PPG are likely to lead to new diagnostic and therapeutic approaches to hypertension and related cardiovascular diseases.